1. Field of Invention
This invention relates to a method and system for distinguishing between displacing targets and a surface of water by transmitting pulses from a transmitter towards the surface of water, the pulses being reflected and received by a receiver. The invention is intended to be used in a proximity fuse arrangement, for torpedoes or mines, for example.
2. Description of Prior Art
The previously known devices use the distance to the surface of the water as a reference, and form in different ways an average surface of the water in order to avoid the problem of false output functions when the sea is high. This leads to several disadvantages since it is very difficult with this method to fulfill the requirement for a low probability of error when the sea is heavy, and at the same time the requirement for a high probability of a correct function when passing the target. It is further required, in the prior art, that the ship's sides be almost vertical in order to get a correct and accurate function.